One-half of the so-called 'It-siblings' alongside Secretary star Maggie, actor Jake Gyllenhaal is about to turn mainstream with $100 million eco-thriller The Day After Tomorrow. A cult star, following the likes of Donnie Darko , Lovely & Amazing , and The Good Girl , the Los Angeles-raised 23-year-old already inspires devotion from internet-based fans who dub themselves 'Gyllenhaalics'. With roles also coming up in John Madden's Proof and Ang Lee's Brokeback Mountain, Jake-mania has only just begun.

Were you worried about taking on a blockbuster like The Day After Tomorrow?

I love big movies and I always have. I love watching them. I've never been a cineaste, preferring just small, independent films. I love big entertainment movies, so it wasn't really a hesitation on my part. It was just whether I would have enough to do - whether it would just be a movie about the weather or be a movie about human relationships with a character you want to watch. I read it and I thought it was awesome.

Have you always been eco-friendly yourself?

I think I was brought up pretty aware of the environment. We had Earth Day at my school, and I was always pretty conscious of it. But I don't think I was ever really conscious of the ramifications for the environment, or more importantly what corporations in the world do, or have done. This film has made me much more aware of how dire it is now, because something like this could happen. When a science fiction director like Roland Emmerich decides to find science fiction in reality, something's wrong. It's a little scary.

So, is there a strong message in amongst all the computer-generated carnage?

I think this movie is really about hope, in a much more profound way than a lot of these big movies are. I feel like I can say that, because I don't do them that much. It's a movie where nobody saves the world, shoots a laser beam and destroys the enemy. It's about us destroying us. In the end, it's about hope, that not everything is destroyed, that we are the most resourceful creatures on Earth and we will figure out a way to live. That is cool. And that's not Hollywood to me. If there's one criticism about Hollywood, it's that they don't make things real. I don't buy that. This is a movie about how we suffer the consequences; what happens to Manhattan in this movie is very hopeful.

So, what was the hardest thing about filming?

Two weeks into the wave scene, when 700 extras were all p***ing into the tank, that was when I said to myself "This seems to be a lot less romantic than I thought!" There's also a scene when the water is rising in a library, and the crew were sinking that room into the water, which had been recycled from the 2½ weeks of us working with extras - and I was putting my head into it that day. The sacrifices I make! But most of it was pretty cool.